Activity Overview

In this activity, students will investigate properties of angles and arcs formed when chords, secants, and tangents intersect and intercept arcs in a circle. They discover several important theorems concerning circles and arc sizes. They make use of the Central Angle theorem, which ensures that the measure of a central angle of a circle is equal to the measure of its intercepted arc.

Before the Activity

Install the Cabri Jr. App on the students' graphing calculators using TI Connect™, a TI Connectivity Cable and the Unit-to-Unit Link Cable

Use the TI-Navigator™ to transfer the attached Cabri Jr. AppVar files to each calculator

See the attached PDF file for detailed instructions for this activity

Print pages 179 - 183 from the attached PDF file for your class

During the Activity

Distribute the pages to your class.

Follow the Activity procedures:

Use the AppVar to go directly to the exploration section

Construct an angle inscribed in a circle and its corresponding central angle

Drag the points and observe changes in the angles

Construct a circle with two intersecting chords

Construct a circle with two secants that intersects outside the circle

Construct a circle which has a tangent and a chord that intersect at a point

Use the Calculate tool to investigate the relationship between the angles formed by the chords